U.S. patent number 5,619,241 [Application Number 08/447,958] was granted by the patent office on 1997-04-08 for ink-jet printing paper and ink-jet printing method using the same.
This patent grant is currently assigned to Fuji Xerox Co., Ltd.. Invention is credited to Kiyoshi Hosoi, Tsukasa Matsuda.
United States Patent |
5,619,241 |
Hosoi , et al. |
April 8, 1997 |
**Please see images for:
( Certificate of Correction ) ** |
Ink-jet printing paper and ink-jet printing method using the
same
Abstract
The printing paper can be formed by applying a slight amount of
paint including a white pigment having a given BET specific surface
area onto at least one side surface of base paper having a given
apparent density. Also, according to the printing paper, in a time
T=L/S to be determined by the shortest inter-nozzle distance L of
different colors of a multi-color ink-jet printer and a printing
paper/head relative moving speed S, the ink absorbing capacity V of
the printing paper according to a blister method satisfies the
following equation: V.gtoreq.2ax.sup.2 /(0.0254).sup.2 (where a
represents an amount of ink drop to be jetted out from a nozzle,
and x represents definition). The present ink-jet printing method
uses the above-mentioned printing paper.
Inventors: |
Hosoi; Kiyoshi (Kanagawa,
JP), Matsuda; Tsukasa (Kanagawa, JP) |
Assignee: |
Fuji Xerox Co., Ltd. (Tokyo,
JP)
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Family
ID: |
16374906 |
Appl.
No.: |
08/447,958 |
Filed: |
May 23, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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84179 |
Jul 1, 1993 |
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Foreign Application Priority Data
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Jul 2, 1992 [JP] |
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4-197462 |
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Current U.S.
Class: |
428/32.37;
428/32.18; 428/32.28 |
Current CPC
Class: |
B41J
2/2121 (20130101); B41M 5/5218 (20130101) |
Current International
Class: |
B41J
2/21 (20060101); B41M 5/52 (20060101); B41M
5/50 (20060101); B41J 002/01 () |
Field of
Search: |
;347/105 ;428/195 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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60-27588 |
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Jun 1985 |
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JP |
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2-16078 |
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Jan 1990 |
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JP |
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2-16079 |
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Jan 1990 |
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JP |
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Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, L.L.P.
Parent Case Text
This application is a continuation of application Ser. No.
08/084,179, filed Jul. 1, 1993, now abandoned.
Claims
What is claimed is:
1. Printing paper for a multi-color, multi-nozzle ink-jet printer
which includes movable printing heads with a nozzle for different
ink colors, each said head having a nozzle jet-out capacity, a,
measured in amount of ink drop (ml), a print definition, x, and an
inter-nozzle distance, L (mm), to ink of different colors and a
printing paper/head relative moving speed, S (mm/s), said paper
comprising:
base paper having an apparent density of 0.60 to 0.80 g/cm.sup.3
and a st ockigt sizing degree of 2 to 18 sec; and
a paint including a white pigment having a BET specific surface
area of 200 to 400 m.sup.2 /g, said paint being applied to at least
one surface of said base paper in such a manner that the amount of
said paint when dried is in the range from 2 to 10 g/m.sup.2, said
paper having an ink absorbing capacity such that in a time T (sec)
to be determined by the shortest inter-nozzle distance L (mm) of
different ink colors of a multi-color ink-jet printer and a
printing paper/head relative moving speed S (mm/s), by the formula
T=L/S, the ink absorbing capacity V (ml/m.sup.2) per unit area of
said printing paper according to a blister method satisfies the
following equation (1):
where a represents the amount of ink drop (ml) jetted out from one
nozzle and x represents definition (dpi).
2. Ink-jet printing paper according to claim 1, filler being mixed
in said base paper at a rate of 5 to 30 weight %.
3. Ink-jet printing paper according to claim 1, said base paper
being made on conditions of basis weight of 50 to 100 g/m.sup.2 and
thickness of 65 to 150 .mu.m.
4. Ink-jet printing paper according to claim 1, said white pigment
having average particle diameter 2 to 15 .mu.m and being mixed in
said paint in a rate of 50 to 85 weight %.
5. Ink-jet printing paper according to claim 1, said base paper
being treated in such a manner that a Beck smoothness is not less
than 25 sec.
6. An ink-jet printing method, characterized in that, when
performing a multi-color, multi-nozzle ink-jet printing operation
by use of water ink in a multi-color, multi-nozzle ink-jet printer
which includes movable printing heads with a nozzle for different
ink colors, each said head having a nozzle let-out capacity, a,
measured in amount of ink drop (ml), a print definition, x, and an
inter-nozzle distance, L (mm), to ink of different colors and a
printing paper/head relative moving speed, S (mm/s), there is used
printing paper which comprises base paper having an apparent
density of 0.60 to 0.80 g/m.sup.3 and a st ockigt sizing degree of
2 to 18 sec and a paint including a white pigment having a BET
specific surface area of 200 to 400 m.sup.2 /g, said paint being
applied to at least one surface of said base paper in such a manner
that the amount of said paint when dried is in the range of from 2
to 10 g/m.sup.2, said paper having an ink absorbing capacity such
that in a time T (sec) to be determined by the shortest
inter-nozzle distance L (mm) of different ink colors of a
multi-color ink-jet printer and a printing paper/head relative
moving speed S (mm/s), by the formula T=L/S, the ink absorbing
capacity V (ml/m.sup.2) per unit area of said printing paper
according to a blister method satisfies the following equation
(1):
where a represents the amount of ink drop (ml) jetted out from one
nozzle and x represents definition (dpi).
7. An ink-jet printing method as set forth in claim 6, wherein, as
said water ink, there is used water ink which has a surface tension
of 40 dyn/cm at a temperature of 20.degree. C.
Description
BACKGROUND OF THE INVENTION
The present invention relates to ink-jet printing paper suited for
obtaining a high quality image free from the mixed color running of
ink and the like, in performing multi-color ink-jet printing by use
of water color ink, and an ink-jet printing method using the same
printing paper.
Conventionally, as ink-jet printing paper, there has been proposed
ink-jet printing paper whose ink absorbing property is improved, in
order to obtain an image of a higher quality.
For example, Japanese Patent Examined Publication No. Sho. 60-27588
discloses a printing paper which is formed by applying a paint
having a higher ink absorbing property (of the order of 11 to 13
g/m.sup.2 in a dry amount of paint) on original paper of a higher
sizing degree.
However, since a relatively large amount of paint is applied to the
printing paper, such printing paper gives different feel and
appearance from so called ordinary paper such as copying paper used
in an office and the like, and such printing paper is expensive.
Further, since the paint layer thus applied is poor in strength,
when it is folded or rubbed, powder drop is easily generated in the
paper. The paper powder can be attached to a feeding roll for the
paper, which can result in the poor paper feeding and also in the
clogged ink-jet head.
In order to solve the above-mentioned problems, as disclosed in
Japanese Patent Laid-Open No. Hei. 2-16079, there is proposed
printing paper in which a paint layer (or, an ink receiving layer)
is formed thin and the roughness factor of the surface of the paint
layer is set not less than 10 ml/m.sup.2 or the Beck smoothness of
the paint layer is set not more than 20 sec. Also, as disclosed in
Japanese Patent Laid-Open No. Hei. 2-16078, there is proposed an
ink-jet printing method using printing paper in which a paint layer
is formed thin (the dry amount of paint is of the order of 0.6 to
10 g/m.sup.2) and the amount of initial transfer of the printing
paper (that is, the ink absorbing capacity in the time of contact,
10 ms, of the printing paper with ink according to a blister
method) is more than the maximum printing density (that is, an
upper limit amount of ink to be applied by a printer).
Concerning the printing paper disclosed in the above-mentioned
Reference No. Hei. 2-16079, the paper is caused to minimize the
amount of paint to be applied (that is, the amount of paint when
dried is approximately 0.6 to 6.0 g/m.sup.2) and to rough the
surface of the paint layer, to thereby prevent powder drop from
generating in the printing paper and prevent an ink running at a
boundary portion of different colors (that is, bleeding) in the
printing. But, specifically, when performing a higher density
printing of a definition of 300 dpi or more at a higher speed,
there arises a problem in the printing paper that mixed color
bleeding occurs in the printing portion where different colors of
ink are superimposed on one another. The reason why such mixed
color bleeding occurs is that, in the higher-speed and higher
density printing, a time period from the printing of a first color
to the printing of a second color is too short and the applied
amount of the ink per unit area becomes large and, therefore, these
two colors cannot be absorbed quickly by only roughening the paint
layer surface thereof. Also, in the printing paper, since the paint
layer surface is roughened, the ink flows into the recessed portion
of the roughened surface, and the ink is disturbed to spread over
the paper surface, which results in the ununiform dot shapes. As a
result, the quality of the image is lowered.
Further, in the printing method disclosed in the above-mentioned
reference No. Hei. 2-16078 as well, when executing a high density
printing with the definition of 300 dpi or more at a higher speed,
there is the mixed color bleeding in the printing portion where
different colors of ink are superimposed.
At the time, the contact time period 10 ms, between the printing
paper and ink according to the blister method regulating the
initial transfer amount of the printing paper used in the printing
method, corresponds to the wetting period of ink on the surface of
the printing paper and such wetting period is greatly influenced by
the roughened state of the surface of the printing paper. For the
reason, in order to make the initial transfer amount of the
printing paper in the contact time period 10 ms larger than the ink
discharge amount in the time of the upper limit of the printing
density, roughness of the printing paper surface must be increased,
with the result that, in the printing paper as well, the ink flows
into the recessed portion of such roughened surface, which makes it
impossible to prevent the mixed color bleeding sufficiently and
also makes ununiform the shapes of dots, so that the quality of the
image is lowered.
SUMMARY OF THE INVENTION
The present invention aims at eliminating the above-mentioned
problems found in the conventional printing paper and printing
method. Accordingly, it is an object of the invention to provide an
ink-jet printing paper which, even when multiple-colors are printed
thereon at a higher speed and at a definition having a higher
density of 300 dpi or more, hardly allows mixed color running to
occur and can provide a higher quality image excellent in the clear
coloring property and definition, and an ink-jet printing method
using the same printing paper.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(a) and FIG. 1(b) are graphical representations of
correlation between the ink absorbing capacity, ink jet-out amount
and mixed color bleeding of the printing paper at respective times
T=0.04 and 0.08.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present inventors have made energetic and repetitional studies
to solve the above problems, specifically on the problem as to the
mixed color bleeding, and have so far confirmed that the mixed
color bleeding is apt to occur in a printing portion especially
where two color rush print images are superimposed. The reason for
this seems to us that, after the first color of ink is printed but
before it is absorbed into the printing paper sufficiently, the
second color of ink is printed in the same position superimposedly
on the first color of ink and, therefore, the second color of ink
is caused to flow over the printed position, that is, the mixed
color is caused to run. We have made further many studies on the
basis of this confirmation and have finally found out that the
mixed color bleeding can be prevented by increasing the ink
absorbing speed into the printing paper and also by increasing the
ink absorbing capacity of the printing paper. In this manner, the
present inventors have developed the present invention.
In order words, the ink-jet printing paper of the invention is
printing paper which includes base paper having an apparent density
of 0.60 to 0.80 g/cm.sup.3 and a paint containing a white pigment
having a BET specific surface area of 200 to 400 m.sup.2 /g applied
onto at least one side surface of the base paper in such a manner
that an amount of the paint when dried shows 2 to 10 g/m.sup.2, and
at the same time which, in a time T (s)=L/S when an ink absorbing
capacity V (ml/m.sup.2) per unit area of printing paper according
to the blister method is determined by the shortest nozzles
distance L (mm) of different colors in a multi-color ink-jet
printer and printing paper/head relative moving speed S (mm/s),
satisfies the following equation (1):
where, a represents an amount of ink drop (ml) to be jetted out
from one nozzle, and x represents a resolution (dpi).
Also, the ink-jet printing method of the invention is characterized
in that, when performing a multi-color ink-jet printing operation
by use of water ink, it uses, as the printing paper thereof, the
ink-jet printing paper having the above-mentioned structure.
Further, the printing method of the invention is characterized in
that, as the water ink mentioned in the above technical means,
there is used water ink which has a surface tension of 40 dyn/cm or
less at a temperature of 20.degree. C.
The above-mentioned equation (1) in the present invention is
established for the following reason: that is, in the case of a
multi-color (full color) ink-jet printer of an ink-jet head moving
type, the mixed color bleeding is influenced by the distance
between the nozzles, printing paper/head relative moving speed, and
ink jet-out amount thereof. Therefore, the present inventors have
found out that, in order to prevent the mixed color bleeding from
occurring, within the shortest time that is taken from the printing
of a first color of ink to the printing of a second color of ink
and that can be determined by the inter-nozzle distance and the
printing paper/head relative moving speed of the printer, the ink
absorbing capacity per unit area of the printing paper may be equal
to or more than the maximum ink jet-out amount of at least 2 colors
to be jetted out per unit area from the printer. That is, this
relationship is represented by the equation (1).
Here, the ink absorbing capacity V of the printing paper, unless
special ink for measurement and time are applied, is measured in
accordance with a blister method which is set forth in J. TAPPI
paper pulp test method No. 51-87. Also, the numeral value 0.0254 in
the above equation is a conversion coefficient which is used to
convert an inch unit in the definition x (dpi=dots/inch) into [mm]
unit.
Referring to FIG. 1, there is shown a relation between the ink
absorbing capacity, ink jet-out amount and mixed color bleeding of
the printing paper under the following conditions.
That is, by use of a multi-color ink-jet printer having a
definition x of 300 dpi, the inventors conducted a test in which
the ink drop amount a (ml) of a nozzle was changed to thereby
change the ink jet-out amount expressed by 2ax.sup.2 /(0.0254) per
unit area into three standards (that is, 15 ml/m.sup.2, 21
ml/m.sup.2, and 25 ml/m.sup.2), the time T (s)=L/S to be determined
by the shortest inter-nozzle distance L (mm) of different colors
and the printing paper/head relative moving speed S (mm/s) was
changed into two standards (that is, 0.04 s, and 0.08 s), and rush
images in two colors of ink were printed by superimposing one on
the other in a total of six kinds of printing paper 1 to 6
respectively having different ink absorbing capacity V according to
a blister method. And, the inventors studied the conditions of
occurrence of the mixed color bleeding in the six kinds of printing
paper. That is, the results of the study on the mutual relationship
between the ink absorbing capacity, ink jet-out amount and mixed
color tuning are shown in FIG. 1.
In FIG. 1, a symbol .circleincircle. shows that the mixed color
bleeding did not occur, .largecircle. shows that the mixed color
bleeding occurred but only slightly, .DELTA. shows that the mixed
color bleeding occurred somewhat, and .times. shows that the mixed
color bleeding occurred.
The ink absorbing property in the six kinds of printing paper was
measured and evaluated also by use of other methods than the
above-mentioned blister method, including a st ockigt size degree
method (JIS-P-8122), Cobb size degree method (JIS-P-8140) and
Clemm's water absorbing degree method (JIS-P-8141). However, none
of the st ockigt size degree, Cobb size degree and Clemm's water
absorbing degree are suited to evaluate the absorbing property in a
short time and, therefore, they cannot be used as a proper
evaluation standard to study a relation between the mixed color
bleeding occurring in a short time and ink absorbing property.
On the other hand, in the blister method, the contact time period
of ink and printing paper can be changed arbitrarily and the water
absorbing property can be evaluated in a short time of the order of
several milliseconds. For this reason, the blister method is suited
to investigate a relation between the mixed color bleeding and ink
absorbing property. In other words, according to the blister
method, it is possible to measure the ink absorbing capacity of the
printing paper in a time necessary from the printing of the first
color of ink to the printing of the second color of ink.
Therefore, here, there was used water ink used in a multi-color
ink-jet printer and the moving speed of the moving speed of the
printing paper was adjusted in such a manner that the measuring
time in the blister method provides the above-mentioned time T
(0.04 s, 0.08 s). After then the ink absorbing capacities in the
respective kinds of the printing paper were found. In particular,
the ink absorbing capacities of the paper 1, paper 2 and paper 3
respectively shown in FIG. 1 (a) were measured under the condition
of T=0.04 s, while the ink absorbing capacities of the paper 4,
paper 5 and paper 6 respectively shown in FIG. 1 (b) were measured
under the condition of T=0.08 s.
As can be understood clearly from the results shown in FIG. 1, the
printing paper in which the mixed color bleeding does not occur in
the ink-jet printing by use of the multi-color ink-jet printer of
the above-mentioned head moving type is one whose ink absorbing
capacity V is equal to or greater than the ink jet-out amount
represented by 2ax.sup.2 /(0.0254).sup.2 in both of the times of
T=0.04 s and 0.08 s.
Also, the present inventors made similar studies on a multi-color
ink-jet printer of a fixed head type in which the head for
injecting the ink is fixed and printing paper is movable, instead
of the above-mentioned head moving type printer. In this case,
similarly, it has been confirmed that no mixed color bleeding
occurs in the printing paper whose ink absorbing capacity V
according to the blister method is equal to or greater than the ink
jet-out amount represented by 2ax.sup.2 /(0.0254) in any of the
time T.
As the base paper forming the printing paper of the invention,
normally, there may be used paper which is mainly formed of wood
pulp and, according to cases, there may be used paper which is
formed of wood pulp mixed with glass fiber, synthetic fiber or the
like. Filler is mixed into the base paper. As the filler, there can
be used white filler such as heavy or light calcium carbonate,
talc, kaolin clay, titanium dioxide, zeolite, white carbon or the
like and, especially, calcium carbonate is preferable because it
can improve the coloring property of color material. The filler is
mixed at a rate of weight percent of 5 to 30%, preferably, weight
percent of 10 to 25%, in order to increase the air gap of the base
paper or improve the opacity of the base paper. When the filler is
mixed at a rate of 30% by weight or greater, then the strength of
the base is lowered greatly and paper powder is generated
greatly.
The base paper has an apparent density of 0.60 to 0.80 g/cm.sup.3,
preferably, in the range of 0.65 to 0.78 g/cm.sup.3. If the
apparent density is less than 0.60 g/cm.sup.3, then the printed
image can be reflected on the other side (which is hereinafter
referred to as back reflection as well) or, when a paint to be
described later is applied to the base member, the binder component
of the paint can permeate into the base paper to thereby lower the
strength of the paint layer. On the other hand, if the apparent
density is greater than 0.80 g/cm.sup.3, then the absorbing speed
of ink is lowered, which makes it easy for the mixed color bleeding
to occur.
The base paper is manufactured in such a manner that its basis
weight is 50 to 100 g/cm.sup.2, preferably, 60 to 90 g/cm.sup.2 and
its thickness is 65 to 150 .mu.m, preferably, 80 to 140 .mu.m. If
the basis weight is less than 50 g/cm.sup.2, then the back
reflection is easy to occur. On the hand, if the basis weight is
greater than 100 g/cm.sup.2, then the stiffness of the paper is
increased to thereby increase the buckling force of the paper,
which makes it easy to invite delivery trouble in the printing
device. Also, similarly, if the paper thickness is less than 65
.mu.m, then the back reflection and the like can occur. On the
other hand, if the paper thickness is greater than 150 .mu.m, then
the stiffness of the paper is increased and thereby the buckling
force thereof is also increased, which makes it easy to invite
delivery trouble in the printing device.
Also, the st ockigt size degree (JIS P 8122) of the base paper is
preferably 2 to 18 sec. and, most preferably, 5 to 15 sec. If the
st ockigt size degree is less than 2 sec., then the back reflection
can occur or the binder of the paint can permeate into the base
paper to thereby reduce the strength of the paint layer. On the
other hand, if the st ockigt size degree is greater than 18 sec.,
then the ink absorbing speed is decreased, with the result that the
mixed color bleeding is easy to occur.
As the paint to be applied to at least one side surface of the base
paper having such a high ink absorbing property, there may be used
a paint including a white pigment which has a BET specific surface
area of 200 to 400 m.sup.2 /g, preferably, 300 to 400 m.sup.2 /g
and an average grain diameter of 2 to 15 .mu.m. As the white
pigment having such properties, for example, non-crystal silica is
best. Also, the white pigment is mixed into the paint 50 to 85% by
weight, preferably, 60 to 80% by weight.
If the BET specific surface area of the white pigment is less than
200 m.sup.2 /g, then the ink absorbing speed in the paint layer is
decreased to thereby facilitate the generation of the mixed color
bleeding, which is unfavorable. And, if the BET specific surface
area is 200 m.sup.2 /g or more, then no mixed color bleeding occurs
at all and the coloring property of the ink is improved. On the
other hand, if the BET specific surface area is greater than 400
m.sup.2 /g, then the hardness of the pigment is lowered to thereby
turn the pigment into a soft pigment, so that it is difficult to
write on the paper with a pencil and the like. Also, if the average
grain diameter of the pigment is less than 2 .mu.m, then it is
difficult to write on the paper with a pencil and the like. On the
other hand, if the average grain diameter is greater than 15 .mu.m,
then the unevenness of the surface of the paint layer is increased
to thereby allow the ink to flow out laterally in the dent, with
the result that the shapes of dots can be made ununiform in
printing and the mixed color bleeding is easy to occur. Further, if
the mixing amount of the white pigment is less than 50% by weight,
then a similar ill effect can be produced as in the above-mentioned
case where the BET specific surface area is less then 200 m.sup.2
/g. On the other hand, if the mixing amount is greater than 85% by
weight, then the strength of the paint layer is decreased, which
facilitates the generation of the powder drop and makes it
difficult to write with a pencil and the like.
Also, since the white pigment such as non-crystal silica and the
like gives a water resisting property, light resistance and the
like, the white pigment may be modified by a metal ion having a
cationic property such as Ca, Al, Mg and the like. Further,
according to objects, there may be mixed a small amount of pigment
which has a BET specific surface area of less than 200 m.sup.2
/g.
As the binder component of the paint, the following can be used
alone or in combination, which includes a polyvinylalcohol
derivative such as completely saponified polyvinylalcohol,
partially saponified polyvinylalcohol, silanol group denatured
vinylalcohol copolymer and the like; a cellulose derivative such as
carboxylmethylcellulose, hydroxyethylcellulose,
hydroxypropylmethylcellulose and the like; and, a water-soluble
macromolecule such as polyvinylpyrrolidone, oxidized starch,
denatured starch, gelatin, casein, acrylic acid system polymer and
the like. Among them, polyvinylalcohol system macromolecule such as
completely saponified polyvinylalcohol, partially saponified
polyvinylalcohol, silanol group denatured vinylalcohol copolymer
and the like is preferable from the point of view of the strength
of the paint layer. Further, silanol group denatured vinylalcohol
copolymer is most preferable due to the fact that it can improve
the strength of the paint layer to thereby be able to increase the
mixing amount of a pigment which is used to catch dye contained in
the ink.
Also, in order to give the water resisting property of the water
ink image to the paint layer, there can be used individually or in
combination amine system macromolecule such as polyethylene-imine,
polyacryl-amine and the like and the quaternary salt thereof,
cationic water macromolecule consisting of a copolymer composed of
an acrylic-system compound and ammonium salt and the like, and
water metal salt. Further, according to needs, a fluorescent
whitening agent, a surface active agent, an anti-mold agent, a
dispersing agent and the like may be added to the paint.
In the printing paper of the invention, the above-mentioned paint
is applied to at least one side surface of the previously described
base paper in such a manner that the dry amount of the paint is 2
to 10 g/m.sup.2, preferably, 3 to 8 g/m.sup.2. If the dry amount of
the paint is less than 2 g/m.sup.2, then the mixed color bleeding
can occur and the resultant paper can lack in the clear coloring
property thereof. On the other hand, if the dry amount of the paint
is greater than 10 g/m.sup.2, then the strength of the paint layer
itself is decreased. As painting means, there can be conveniently
employed a reverse coater, an air knife coater, a blade coater, a
gate roll coater and the like.
Also, in the present invention, in order that a dot to be printed
on the printing paper is near a true circle in shape and is not so
rough, according to needs, the surface of the printing paper may be
finished by means of a super calender processing or the like in
such a manner that the Beck smoothness thereof is 25 sec. or more,
preferably, in the range of 25 to 100 sec., provided that the given
apparent density (0.60 to 0.80 g/cm.sup.3) of the base paper is
secured.
The printing method of the invention, basically, is a method to be
performed by applying the above-structured ink-jet printing paper
to a conventionally known ink-jet printing method using water ink.
The present printing method can prevent the mixed color bleeding
from occurring especially when a multi-color printing is executed,
and can also provide an image which is excellent in the coloring
property, clearness, and definition.
Also, according to the printing method of the invention, by using
water ink which has a surface tension of 40 dyn/cm or less,
preferably, in the range of 25 to 40 dyn/cm, more preferably, in
the range of 30 to 40 dyn/cm at a temperature of 20.degree. C., it
is possible to prevent the occurrence of the mixed color bleeding
more surely when a multi-color printing operation is executed and,
at the same time, it is possible to obtain an image of high quality
which is further excellent in the coloring property, clearness, and
definition thereof.
Therefore, if ink having a surface tension of greater than 40
dyn/cm is used, in some cases the occurrence of the mixed color
bleeding can be prevented to some degree, while in most cases the
mixed color bleeding occurs. On the other hand, if the surface
tension of ink to be used is less than 30 dyn/cm, then the
jetting-out of ink from a head nozzle is easy to be unstable, and
the usable select width of an ink-jet head is limited. Further, if
the ink surface tension is less than 25 dyn/cm, then the poor
jetting-out of ink from the head nozzle is easy to occur.
As the dye of the water ink to be used in the present printing
method, there can be used water-soluble acid dye, direct dye, basic
dye, reactive dye, food color and the like which have been
conventionally known. Also, the content of the dye in the ink may
be 0.5 to 15% by weight, preferably, 1 to 10% by weight.
Also, with respect to a solvent for the water ink, water which is
demineralized may be preferably used as a main solvent. And, it is
preferable that a humidity keeping agent may be contained in the
solvent mainly in order to prevent the solvent from being dried in
the head nozzle. As the humidity keeping agent, for example, there
can be used polyvalent alcohol such as ethyleneglycol,
diethyleneglycol and the like, but this is not always
limitative.
The surface tension of ink can be adjusted by adding a proper
amount of a surface tension adjusting agent to the solvent. As the
surface tension adjusting agent, there can be used various kinds of
adjusting agents and, preferably, two kinds of adjusting agents may
be pointed out which are mainly classified as follows:
(1) Anionic surface active agents such as higher alcohol sulfate,
higher alkyl ether sulfate, alkyl benzene sulfonate, .alpha.-olefin
sulfonate, phosphate of higher alcohol ethylene oxide addition
product and the like. Cationic surface active agents such as amine
salt type, quaternary ammonium salt type and the like. Amphoteric
surface active agents such as an amino acid type, a betaine type
and the like. Nonionic surface active agents such as a higher
alcohol ethylene oxide addition product, an alkyl phenol ethylene
oxide addition product, a fatty acid ethylene oxide addition
product, an ethylene oxide addition product of higher aliphatic
amine and fatty acid amide, fatty acid ester of glycerol and
pentaerythritol, fatty acid ester of sugar, fatty acid alkanol
amid, an oxidized ethylene/oxidized propylene block copolymer and
the like. Silicone-system and fluorine-system ionic and nonionic
surface active agents.
(2) Materials which are normally not classified as surface active
agents but are believed to have a weak surface active performance,
having a water soluble portion or a hydrophilic portion whose
surface tension is about 40 dyn/cm or less, preferably, about 35
dyn/cm or less. For example, propylene glycol, polypropylene
glycol. Ether such as alkyl or alkyl phenyl of polyhydric alcohol
of ethylene glycol, di-ethylene glycol, tri-ethylene glycol,
tetra-ethylene glycol, propylene glycol, glycerol and the like.
Acid derivatives such as ethylene carbonate, propylene carbonate,
ether lactate and the like. Various kinds of alcohols such as
isopropyl alcohol, n-butyl alcohol, 2-butanol, isobutyl alcohol,
tert-butyl alcohol, pentanols, benzyl alcohol, cyclohexanol, and
the like.
In the case of the water ink that is jetted out as ink liquid
droplets from the ink-jet head nozzles, in a process where the ink
droplets contact with the surface of the printing paper and then
permeate into the printing paper, the surface areas of the ink
droplets are increased suddenly and sharply. For this reason, even
if the surface tension of the ink is adjusted in the ink adjusting
process such that it is 40 dyn/cm or less, when the surface tension
of the ink in the interface between the ink and printing paper when
the ink permeates into the printing paper exceeds 40 dyn/cm
effectively, then the effect of the invention is caused to
decrease. In view of this, in order to perform the effect of the
invention to the full, even when the ink permeates into the
printing paper, it is desirable that the ink should be adjusted
such that the surface tension of the ink in the interface between
the ink and printing paper can continue to be about 40 dyn/cm. In
fact, it is difficult to measure the ink surface tension in the
interface between the ink and printing paper when the ink permeates
into the printing paper. To secure such desirable ink surface
tension, the amount of addition of a surface tension adjusting
agent may be set properly in consideration of the following
phenomena results.
In other words, in general, when a surface active agent is added to
ink, the surface tension of the ink becomes constant if the
additive concentration (amount) of the surface active agent is
equal to or greater than a critical micell concentration (c.m.c.).
However, in the case of two kinds of ink which have the same
surface tension under the condition that the additive concentration
of the surface active agent is equal to or greater than the
critical micell concentration, it is confirmed that the effects of
the invention can be achieved more sufficiently in the ink having a
higher concentration of the surface active agent than the ink
having a lower concentration of the surface active agent. Of
course, in this case, if the surface tension adjusting agent is
added too much, then air bubbles are generated, ink jetting-out is
worsened, and the ink is spread too excessively. This causes
secondary obstacles: that is, the resolution of the printed image
is lowered; the ink is caused to permeate into the printing paper
too much, so that the ink can run through to the back side of the
printing paper; and, the coloring density is worsened. Therefore,
in order to avoid these problems, the concentration of addition of
the surface tension adjusting agent must be examined
deliberately.
Although it is difficult to regulate the amount of addition of the
surface tension adjusting agent partly because the effect of the
addition thereof varies according to the chemical structure
thereof, in general, in the case of the surface tension adjusting
agents which belong to the above-mentioned (1) group, about 0.1 to
5% by weight, preferably, about 0.8 to 2.0% by weight with respect
to ink may be selected; and, in the case of the surface tension
adjusting agents which belong to the (2) group, about 1 to 40% by
weight, preferably, about 2 to 15% by weight may be selected. Of
course, in the present invention, two or more kinds of surface
tension adjusting agents belonging to the above-mentioned (1) and
(2) groups can be combined and however, in this case as well, the
amount of addition of such combined surface tension adjusting
agents should be set properly in accordance with the
above-mentioned amount of addition.
Besides the above-mentioned components, an anti-molding agent, a
viscosity adjusting agent, a pH adjusting agent and the like can be
added to the water ink.
Also, it is not specially necessary to regulate the viscosity of
the water ink but, from the viewpoint of the ink jet-out stability
and the image characteristic, the viscosity of the water ink at a
temperature of 20.degree. C. is preferably 1 to 8 cp and, more
preferably, it is 1 to 5 cp.
For example, when images are printed on the printing paper of the
invention by use of the water ink which has a surface tension of 40
dyn/cm or less, then good images can be formed and, at the same
time, on ordinary paper including transfer paper for electronic
photography such as L paper produced by Fuji Xerox (Co.) as well,
there can be formed images in which the ink drying time is about 10
sec. or less when rush print images (1 cm.times.cm) are
printed.
Due to the fact that the printing paper of the invention allows ink
to be absorbed at a high speed and provides a large amount of ink
absorbing capacity, even when a multi-color ink-jet printing
operation is executed at a high speed and at a high density, the
mixed color bleeding can be prevented sufficiently. Also, since the
dye contained in the ink to be jetted out from the head nozzle can
be caught effectively by the air gap of a white pigment having a
high specific surface area in the paint layer of the printing
paper, there can be provided a fresh coloring property and suitable
dot spreading, so that there can be obtained images of high
quality. Also, because the amount of paint to be applied when the
paint layer is formed is slight, there can be obtained printing
paper whose paint layer is excellent in strength and whose feeling
and appearance are both almost similar to those of ordinary
paper.
In addition, due to the fact that, in the above mentioned printing,
by using the water ink whose surface tension at a temperature of
20.degree. C. is 40 dyn/cm or less, the wettability of the ink
relative to the base paper can be improved, the absorbing speed of
ink into the base paper can be further enhanced and the mixed color
bleeding can be prevented, so that there can be obtained more
surely a high quality of image which is excellent in the coloring
property and definition.
Description will be given below in more detail of the present
invention by way of embodiment and comparisons. However, the
invention is not limited to these embodiments.
[Manufacture of Printing Paper A to K]
A paper material including a filler and a size agent which are of
the kind and content to be shown below was added to LBKP base pulp,
which had been beat to a freeness of 500 ml C.S.F., in such a
manner that an basis weight, a thickness and an apparent density as
shown in Table 1 could be obtained, and the resultant product was
considered as the paper. Also, in Table 1, there are shown the st
ockigt size degrees of the respective sheets of base paper.
Filler
Printing Paper A: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper B: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper C: Kaolin clay (AA Kaolin, Sanyo Clay Industry)--10%
by weight
Printing Paper D: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper E: Kaolin clay: AA Kaolin (Sanyo Clay Industry)--10%
by weight
Printing Paper F: Heavy calcium carbonate (Softon 1800, Bihoku
Funka Industry)--15% by weight
Printing Paper G: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper H: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper I: Light calcium carbonate (TP 121, Okutama
Industry)--15% by weight
Printing Paper J: Heavy calcium carbonate (Softon 1800, Bihoku
Funka Industry)--15% by weight
Printing Paper K: Heavy calcium carbonate (Softon 1800, Bihoku
Funka Industry)--15% by weight
Size Agent
Printing Paper A: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper B: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper C: Rosin size (Size pine E, Arakawa Chemical
Industry)--0.1% by weight
Printing Paper D: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper E: Alkynol succinic anhydride system size agent
(Five run 81, Ohji National)--0.05% by weight
Printing Paper F: Alkynol succinic anhydride system size agent
(Five run 81, Ohji National)--0.05% by weight
Printing Paper G: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper H: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper I: Alkyl ketene dimer system size agent (Sylene 70,
Kao)--0.04% by weight
Printing Paper J: Alkynol succinic anhydride system size agent
(Five run 81, Ohji National)--0.04% by weight
Printing Paper K: Alkynol succinic anhydride system size agent
(Five run 81, Ohji National)--0.06% by weight.
Next, a paint solution composed of a white pigment, a binder and a
water resisting agent, whose kind and content will be described
below, was applied by a bar coater onto each of the base paper in
such a manner that the paint had its dry weight as shown in Table
1, and after then the paint layer was finished so that the Beck
smoothness of the surface of the pain layer had the following
value, whereby there were obtained ink-jet printing paper A to G
(embodiments) and H to K (comparisons). The BET specific areas of
the respective white pigments are also shown in Table 1.
White Pigment
Printing Paper A: Fine grain synthesis non-crystal silica
(Mizucasil P-802, Mizusawa Chemical Industry)--72% by weight
Printing Paper B: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry)--72% by weight
Printing Paper C: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry)--72% by weight
Printing Paper D: Silica (Mizucasil P-802, Mizusawa Chemical
Industry)--72% by weight
Printing Paper E: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry)--72% by weight
Printing Paper F: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry) 72% by weight
Printing Paper G: Silica (Mizucasil P-526N, Mizusawa Chemical
Industry)--72% by weight
Printing Paper H: Silica (Mizucasil P-526N, Mizusawa Chemical
Industry)--72% by weight
Printing Paper I: Silica (Mizucasil P-526N, Mizusawa Chemical
Industry)--72% by weight
Printing Paper J: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry)--72% by weight
Printing Paper K: Silica (Mizucasil P-78D, Mizusawa Chemical
Industry)--72% by weight
Binder
Printing Paper A: Completely saponified poly-(vinyl alcohol) (PVA
117, Kuraray)--23% by weight
Printing Paper B: Completely saponified poly-(vinyl alcohol) (PVA
117, Kuraray)--23% by weight
Printing Paper C: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Printing Paper D: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Printing Paper E: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Printing Paper F: Completely saponified poly-(vinyl alcohol) (PVA
117, Kuraray)--23% by weight
Printing Paper G: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Printing Paper H: Completely saponified poly-(vinyl alcohol) (PVA
117, Kuraray)--23% by weight
Printing Paper I: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Printing Paper J: Completely saponified poly-(vinyl alcohol) (PVA
117, Kuraray)--23% by weight
Printing Paper K: Silanol group denatured vinyl alcohol copolymer
(PVA 2130, Kuraray)--23% by weight
Water Resisting Agent
Printing Paper A: Water cation polymer (PAS-J11, Nittobo)--5% by
weight
Printing Paper B: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper C: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper D: Water cation polymer (PAS-J11, Nittobo)--5% by
weight
Printing Paper E: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper F: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper G: Water cation polymer (PAS-J11, Nittobo)--5% by
weight
Printing Paper H: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper I: Water cation polymer (PAS-J11, Nittobo)--5% by
weight
Printing Paper J: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Printing Paper K: Water cation polymer (Epomin P1000, Nihon
Shokubai Industry)--5% by weight
Beck Smoothness
Printing Paper A: 28 sec., Printing Paper B: 30 sec.,
Printing Paper C: 30 sec., Printing Paper D: 31 sec.,
Printing Paper E: 32 sec., Printing Paper F: 34 sec.,
Printing Paper G: 35 sec., Printing Paper H: 30 sec.,
Printing Paper I: 32 sec., Printing Paper J: 35 sec.,
Printing Paper K: 36 sec.
TABLE 1
__________________________________________________________________________
Printing paper (Embodiment) Printing paper (Comparison) A B C D E F
G H I J K
__________________________________________________________________________
Base Paper Basis weight (g/m.sup.2) 65 70 70 70 81 72 71 70 70 75
81 Thickness (g/m.sup.2) 100 100 100 100 109 91 90 100 100 90 90
Apparent density (g/cm.sup.3) 0.65 0.70 0.70 0.70 0.74 0.79 0.79
0.70 0.70 0.83 0.90 St ockigt sizing degree 9 9 3 9 8 10 9 30 9 8
14 Paint layer Pigment BET specific 300 300 200 200 300 300 200 300
100 300 300 surface area Dry amount of paint 6 6 6 6 6 6 6 6 6 8 6
applied (g/m.sup.2)
__________________________________________________________________________
[Preparation of Water Ink A to C]
There were obtained ink sets A to C which are composed of the
following kinds and contents of dyes and solvents of kinds and
contents shown in Table 2. The surface tensions of the respective
ink in the sets are also shown in Table 2.
TABLE 2 ______________________________________ Dye Black Ink: C.I
Acid Black 56 2.5% by weight Cyan Ink: C.I Acid Blue 2.5% by weight
Magenta Ink: C.I Direct Red 2.5% by weight Yellow Ink: C.I Direct
yellow 2.5% by weight Composition of Solvent Surface tension
(Content: Weight %) (dyn/cm) ______________________________________
Ink set A Water (77) Black ink 37 Ethylene glycol (12) Cyan ink 38
Di-ethylene glycol Magenta ink 37 Monobutyl ether (85) Yellow ink
36 Ink set B Water (77) Black ink 54 Di-ethylene glycol (20.5) Cyan
ink 53 Magenta ink 55 Yellow ink 52 Ink set C Water (73) Black ink
32 Di-ethylene glycol (20) Cyan ink 31 Isopropyl alcohol (3.5)
Magenta ink 32 Alkyl naphthalene Yellow ink 31 sulfonic acid Na (1)
______________________________________
[Embodiments 1 to 21, Comparisons 1 to 12]
A color recording test was conducted using the combination of the
above-mentioned printing paper A to K and ink sets A to C which
were combined in such a manner as shown in Table 3, as well as by
use of a multi-color inkjet printer, that is, a printing device
which includes four printing heads for black, cyan, Magenta and
yellow each having a nozzle average jet-out capacity a=75 (ml), had
a printing density performance of 300 dpi, the shortest
inter-nozzle distance L to ink of different colors L=20 (mm) and
head moving speed S=381 mm/s, and ink jet-out amount=20.9
ml/m.sup.2 which can be expressed by 2ax.sup.2 /(0.0254).sup.2
under the condition of T=L/S=0.52 sec.
On the images obtained in this manner, the fresh coloring property,
definition and the strength of the paint layer were respectively
studied and evaluated. Also, the ink absorbing capacity of the
respective printing paper were respectively measured according to a
method which is described below.
The results of the ink absorbing capacity and evaluations are shown
in Table 3.
[Measurement of Ink Absorbing Capacity]
The ink absorbing capacity of the respective printing paper was
measured by use of a dynamic liquid permeability testing machine
(manufactured by Toyo Seiki Mfg.) according to the blister method
of J. TAPPI.
That is, there was used a head box which has a slit dimension of 1
mm.times.15 mm, and the load to be applied to the head was set for
0.5 kg/cm.sup.2. Also, the absorbing time in the testing machine
was set for 0.052 (s) in order to be identical with the time T=L/S
which can be determined by the shortest inter-nozzle distance L
(mm) of different colors of the above-mentioned printer and the
head moving speed S (mm/s). As the measuring liquid, there was used
the cyan ink of the respective ink sets A to C to be actually
combined and used. The ink absorbing capacity was measured under
these conditions.
With respect to the mixed color bleeding, a rush image printed with
Magenta ink and formed in a square having each side of 1 cm was
printed superimposedly on the central portion of a rush image
printed with cyan ink and formed in a square having each side of 2
cm, the super-imposed portion thereof was visually observed and
confirmed in such a manner that the bleeding in the boundary
portion between the cyan and red was considered as the mixed color
bleeding in view of the fact that the superimposed portion becomes
colored red in accordance with a subtractive mixture rule, and then
the mixed color bleeding was evaluated on the basis of the
following standards. That is, .circleincircle.: No mixed color
bleeding occurred, .largecircle.: Slight mixed color bleeding
occurred, .DELTA.: Small mixed color bleeding occurred, and
.times.: Mixed color bleeding occurred.
The coloring and clearness were confirmed by visually observing the
color images and then were evaluated on the basis of the following
standards. That is, .circleincircle.: Very good, .smallcircle.:
Good, .DELTA.: Ordinary, and x: Poor.
With respect to the definition, letters (dense), and (wealth) were
printed in Ming-style type and the understandability of the
characters and then the qualities thereof were visually judged and
were evaluated on the basis of the following standards. That is,
.circleincircle.: Understandability and quality of character are
both very good, .largecircle.: Understandability and quality are
both good, .DELTA.: Character is somewhat defaced, and .times.:
Character is defaced.
With respect to the strength of the paint layer, the printing paper
was folded, a metal roll of 2 kg was rolled on the folded portion
of the printing paper, and the degree of peeling of the paint layer
was evaluated on the basis of the following standards. That is,
.circleincircle.: Paint layer did not peel at all, .largecircle.:
Paint layer peeled slightly, .DELTA.: Paint layer peeled somewhat,
and .times.: Paint layer peeled fairly.
TABLE 3
__________________________________________________________________________
Ink absorbing Mixed Clear Print Printing capacity color coloring
layer paper Ink set (ml/m.sup.2) bleeding property defini-tion
strength
__________________________________________________________________________
Embodiment 1 A A 34 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 2 B " 31
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 3 C " 32 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 4 D " 26
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 5 E " 28 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 6 F " 24 .smallcircle.
.smallcircle. .smallcircle. .circleincircle. Embodiment 7 G " 21
.smallcircle. .smallcircle. .smallcircle. .circleincircle.
Embodiment 8 A B 28 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 9 B " 26
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 10 C " 27 .circleincircle. .smallcircle.
.circleincircle. .circleincircle. Embodiment 11 D " 24
.smallcircle. .smallcircle. .smallcircle. .circleincircle.
Embodiment 12 E " 24 .smallcircle. .smallcircle. .smallcircle.
.circleincircle. Embodiment 13 F " 22 .smallcircle. .smallcircle.
.DELTA. .circleincircle. Embodiment 14 G " 21 .smallcircle.
.smallcircle. .DELTA. .circleincircle. Embodiment 15 A C 37
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 16 B " 34 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 17 C C 35
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 18 D " 29 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 19 E " 30
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Embodiment 20 F " 27 .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Embodiment 21 G " 24
.smallcircle. .smallcircle. .smallcircle. .circleincircle.
Comparison 1 H A 14 x .smallcircle. x .circleincircle. Comparison 2
I " 12 x .DELTA. x .circleincircle. Comparison 3 J " 13 x
.smallcircle. x .smallcircle. Comparison 4 K " 12 x .smallcircle. x
.circleincircle. Comparison 5 H B 11 x .smallcircle. x
.circleincircle. Comparison 6 I " 10 x .DELTA. x .circleincircle.
Comparison 7 J " 10 x .smallcircle. x .smallcircle. Comparison 8 K
" 10 x .smallcircle. x .circleincircle. Comparison 9 H C 16 x
.smallcircle. .DELTA. .circleincircle. Comparison 10 I " 14 x
.DELTA. x .circleincircle. Comparison 11 J " 15 x .smallcircle.
.DELTA. .smallcircle. Comparison 12 K " 14 x .smallcircle. x
.circleincircle.
__________________________________________________________________________
As has been described heretofore, according to the invention, even
when a multi-color ink-jet printing is executed at a high speed and
at a high density, little mixed color bleeding occurs and there can
be obtained an image of high quality which is excellent in the
clear coloring property and definition. Also, according to the
printing paper of the invention, since a slight amount of specific
paint is applied to form a paint layer and thus the paint layer has
a great strength, there is eliminated the possibility that the
paper powder drop occur. Thus, the present printing paper is
inexpensive in the cost thereof involved in the manufacturing
process and also provides the feeling and appearance that are
similar to ordinary paper.
Also, according to the invention, in the ink-jet printing using the
present printing paper, by using water ink having a specific
surface tension, the occurrence of the mixed color bleeding can be
prevented for sure and there can be obtained an image which is more
excellent in the fresh coloring property and definition.
* * * * *